Liquid crystal display device

ABSTRACT

There is disclosed a liquid crystal display device comprising an array substrate, an counter substrate, and a liquid crystal layer which is held between the array substrate and the counter substrate and whose liquid crystal molecular arrangement is divided into a plurality of pixel areas controlled by the array substrate and opposite substrate. The array substrate includes a reflective pixel electrode for scattering a light incident via the counter substrate and liquid crystal layer. The reflective pixel electrode has a reflective surface in which a first undulation having a gradual inclined surface disposed in each pixel area and a second undulation having a plurality of convex portions as main scattering portions disposed in each pixel area are superimposed.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims the benefit of priorityfrom the prior Japanese Patent Applications No. 2000-333722, filed Oct.31, 2000; and No. 2001-110450, filed Apr. 9, 2001, the entire contentsof both of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a liquid crystal display device,particularly to a reflective liquid crystal display device having areflection function, and a semi-transmission type liquid crystal displaydevice having a reflection function and transmission function.

[0004] 2. Description of the Related Art

[0005] In recent years, a liquid crystal display device has been appliedto various apparatuses such as a personal computer, television, wordprocessor, and mobile phone. An application range of the liquid crystaldisplay device has been broadened, whereas a demand for enhancedfunctions such as a small size, power saving, and low cost isincreasing. To satisfy this demand, development of a reflective liquidcrystal display device has been advanced. Since the reflective liquidcrystal display device uses an external light to display an image, aninternal light source such as a back light unit is not required.

[0006] In the reflective liquid crystal display device, the externallight is reflected by a reflective plate and optically modulated by aliquid crystal layer so that the image is displayed. A brightness of theexternal light depends on an installation environment of the liquidcrystal display device, and is not stable as in a back light. Therefore,to prevent a light intensity of the external light from being attenuatedas much as possible is important for display of a bright image.Particularly, a reflection property of the reflective plate largelyinfluences the attenuation of the light intensity. Therefore,optimization is attempted in order to obtain the reflection property forefficiently reflecting the external light incident at any angle.

[0007] As one example of the optimization, it is proposed to dispose anundulation on a reflective surface of the reflective plate as shown inFIG. 10. That is, the undulation of the reflective surface controlsscattering of a reflected light so as to concentrate the reflected lightin a certain range of area, and raise a reflected light intensity withrespect to a specific observation direction.

[0008] In actual manufacturing, the reflective surface having theaforementioned undulation is obtained by disposing the reflective plateon a main scattering portion including a plurality of irregularlyarranged circular protrusions. The reflection property of the reflectiveplate is substantially optimum, when a diameter d of the protrusion isset to a range of 3 to 20 μm, and a height H of the protrusion is set toa range of 0.6 to 1.2 μm. However, when the undulation of the reflectivesurface, that is, a difference of elevation exceeds 1 μm by theaforementioned structure with respect to a small lateral width of about10 μm, this induces an alignment defect of a liquid crystal, and animage contrast is deteriorated.

[0009] As a countermeasure, if the difference of elevation of thereflective surface is limited to about 0.5 μm with respect to theaforementioned lateral width, the deterioration of an image quality canbe avoided. However, when such countermeasure is taken, an inclinationangle of the reflective surface decreases. Therefore, the reflectedlight intensity in the vicinity of regular reflection relativelyincreases. As a result, a range of an angle of a field of view in whicha sufficient reflected light intensity is obtained is narrowed. That is,this countermeasure is not practical because the reflection property ofthe reflective plate is not optimized.

BRIEF SUMMARY OF THE INVENTION

[0010] The present invention has been developed in consideration of theaforementioned problem, and an object thereof is to provide a liquidcrystal display device which can prevent an alignment defect of a liquidcrystal without deteriorating a satisfactory optical property and whichhas a high contrast and a satisfactory display quality level.

[0011] To solve the problem and achieve the object, there is provided aliquid crystal display device comprising: first and second electrodesubstrates; and a liquid crystal layer which is held between the firstand second electrode substrates and whose liquid crystal moleculararrangement is divided into a plurality of pixel areas controlled by thefirst and second electrode substrates,

[0012] wherein the first electrode substrate includes a reflective platefor scattering a light incident via the second electrode substrate andthe liquid crystal layer, and

[0013] the reflective plate has a reflective surface in which a firstundulation formed by disposing a gradual inclined surface in each pixelarea and a second undulation formed by disposing a plurality of mainscattering portions in each pixel area are superimposed.

[0014] Moreover, there is provided a liquid crystal display devicecomprising: first and second electrode substrates; and a liquid crystallayer which is held between the first and second electrode substratesand whose liquid crystal molecular arrangement is divided into aplurality of pixel areas controlled by the first and second electrodesubstrates,

[0015] wherein the first electrode substrate includes an area in which areflective plate for scattering a light incident via the secondelectrode substrate and the liquid crystal layer is formed and which hasa reflection function, and an area having a transmission function fortransmitting the light incident via the first electrode substrate, and

[0016] the reflective plate has a reflective surface in which a firstundulation formed by disposing a gradual inclined surface in each pixelarea and a second undulation formed by disposing a plurality of mainscattering portions in each pixel area are superimposed.

[0017] In the liquid crystal display device, the reflective plate hasthe reflective surface in which the first undulation formed by disposingthe gradual inclined surface in each pixel area and the secondundulation formed by disposing the plurality of main scattering portionsin each pixel area are superimposed. That is, the main scatteringportion of the second undulation controls scattering of the reflectedlight on the gradual inclined surface obtained by the first undulationwith respect to each pixel area.

[0018] In this case, even when a difference of elevation of the secondundulation is limited with respect to a micro lateral width, aninclination angle of the reflective surface is not reduced, and areflection property of the reflective plate can be maintained to beoptimum by superimposition of the first and second undulations. In otherwords, an alignment defect of a liquid crystal can be prevented withoutdeteriorating a satisfactory optical property, that is, reflectionproperty. As a result, the liquid crystal display device can display ahigh-quality image which has a broad angle of field of view and a highcontrast.

[0019] Additional objects and advantages of the invention will be setforth in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention. Theobjects and advantages of the invention may be realized and obtained bymeans of the instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0020] The accompanying drawings, which are incorporated in andconstitute a part of the specification, illustrate embodiments of theinvention, and together with the general description given above and thedetailed description of the embodiments given below, serve to explainthe principles of the invention.

[0021]FIG. 1 is a diagram showing a sectional structure in the vicinityof a pixel of a reflective liquid crystal display device according to afirst embodiment of the present invention.

[0022]FIG. 2 is a diagram showing a plane structure in the vicinity ofthe pixel shown in FIG. 1.

[0023]FIG. 3 shows a sectional structure taken along line III-III shownin FIG. 2.

[0024]FIGS. 4A to 4H are diagrams showing manufacturing steps of anarray substrate shown in FIG. 1.

[0025]FIG. 5 is a diagram showing the plane structure in the vicinity ofthe pixel of the reflective liquid crystal display device according to asecond embodiment of the present invention.

[0026]FIG. 6 is a diagram showing a sectional structure taken along lineVI-VI shown in FIG. 5.

[0027]FIG. 7 is a diagram showing the plane structure in the vicinity ofthe pixel of the reflective liquid crystal display device according to athird embodiment of the present invention.

[0028]FIG. 8 is a diagram showing a sectional structure taken along lineVIII-VIII shown in FIG. 7.

[0029]FIGS. 9A to 9J are diagrams showing the manufacturing steps of thearray substrate of the reflective liquid crystal display deviceaccording to a fourth embodiment of the present invention.

[0030]FIG. 10 is a diagram showing the sectional structure of a pixelperipheral surface of a conventional reflective liquid crystal displaydevice.

[0031]FIG. 11 is a diagram showing the sectional structure in thevicinity of the pixel of a semi-transmission type liquid crystal displaydevice according to a fifth embodiment of the present invention.

[0032]FIG. 12 is a diagram showing the plane structure in the vicinityof the pixel shown in FIG. 11.

[0033]FIG. 13 shows a sectional structure taken along line A-B shown inFIG. 12.

[0034]FIGS. 14A to 14H are diagrams showing manufacturing steps of thearray substrate shown in FIG. 11.

[0035]FIG. 15 is a diagram showing the sectional structure in thevicinity of the pixel of the semi-transmission type liquid crystaldisplay device according to a sixth embodiment of the present invention.

[0036]FIG. 16 is a diagram showing the sectional structure in thevicinity of the pixel of the semi-transmission type liquid crystaldisplay device according to a seventh embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

[0037] A liquid crystal display device according to one embodiment ofthe present invention will be described hereinafter with reference tothe drawings.

[0038]FIG. 1 shows a sectional structure in the vicinity of a pixel of areflective liquid crystal display device according to a first embodimentof the liquid crystal display device, FIG. 2 shows a plane structure inthe vicinity of the pixel of the reflective liquid crystal displaydevice, and FIG. 3 shows a sectional structure taken along line III-IIIshown in FIG. 2. The liquid crystal display device includes an arraysubstrate 10, an counter substrate 11, and a liquid crystal layer 12held between these substrates 10 and 11.

[0039] The array substrate 10 includes an insulating substrate 13, aplurality of reflective pixel electrodes 23 arranged in a matrix form, aplurality of signal lines 14 arranged along a row of these reflectivepixel electrodes 23, a plurality of scanning lines 15 arranged along aline of these reflective pixel electrodes 23, a plurality of thin filmtransistors for pixels (TFT) 24 arranged as switching elements in thevicinity of intersection positions of the corresponding scanning line 15and signal line 14, and an alignment film 31 with which the plurality ofreflective pixel electrodes 23 are coated.

[0040] The counter substrate 11 includes an insulating substrate 36having permeability to light, a coloring layer 37 forming a color filterwith which the insulating substrate 36 is coated, a transparent counterelectrode 38 with which the coloring layer 37 is coated, and analignment film 39 with which the counter electrode 38 is coated.Moreover, a polarization plate 40 is attached to the transparentinsulating substrate 36 on a side opposite to the coloring layer 37.

[0041] The liquid crystal layer 12 is divided into a plurality of pixelareas PX for the plurality of reflective pixel electrodes 23. Each pixelarea PX is disposed between two adjacent scanning lines 15 and twoadjacent signal lines 14. Each thin film transistor 24 becomesconductive in response to a scanning pulse supplied from thecorresponding scanning line 15, and supplies a potential of thecorresponding signal line 14 to the corresponding reflective pixelelectrode 23. Each reflective pixel electrode 23 applies the potentialof the corresponding signal line 14 as a pixel potential to thecorresponding pixel area PX of the liquid crystal layer 12, and controlsa transmittance of the pixel area PX based on a difference between thepixel potential and the potential of the counter electrode 38.

[0042] In the array substrate 10, each TFT 24 includes a semiconductorlayer 16 of amorphous silicon or polysilicon, a gate electrode 18 formedabove the semiconductor layer 16 in an insulated manner and connected tothe corresponding scanning line 15, and source and drain electrodes 19,20 which contact a source area 16S and drain area 16D of thesemiconductor layer 16 via contact holes 21, 22 on opposite sides of thegate electrode 18 and which are connected to the correspondingreflective pixel electrode 23 and corresponding signal line 14,respectively.

[0043] The semiconductor layer 16 is formed on the insulating substrate13, and coated with a gate insulating film 17 together with theinsulating substrate 13. The gate electrode 18 is insulated from thesemiconductor layer 16 by the gate insulating film 17, and integrallyformed with the corresponding scanning line 15 on the gate insulatingfilm 17. The gate electrode 18 and scanning line 15 as well as the gateinsulating film 17 are coated with an interlayer insulating film 32.

[0044] The contact holes 21, 22 are formed in the interlayer insulatingfilm 32 and gate insulating film 17 so that the source area 16S anddrain area 16D formed in the semiconductor layer 16 are exposed on theopposite sides of the gate electrode 18. The source electrode 19 anddrain electrode 20 are in contact with the source area 16S and drainarea 16D of the semiconductor layer 16 in these contact holes 21, 22,respectively, and formed on the interlayer insulating film 32.

[0045] The source electrode 19 is integrally formed with an expansionsource electrode 33 on the interlayer insulating film 32. The drainelectrode 20 is integrally formed with the corresponding signal line 14on the interlayer insulating film 32. The source electrode 19, expansionsource electrode 33, drain electrode 20, and signal line 14, togetherwith the interlayer insulating film 32, are coated with a protectiveinsulating film 25.

[0046] The protective insulating film 25 has a contact hole 29 in whichthe expansion source electrode 33 is partially exposed, and is coatedwith an organic insulating film 26. The organic insulating film 26 has acontact hole 30 in which the expansion source electrode 33 is partiallyexposed, and the contact hole 30 is formed in the contact hole 29 of theprotective insulating film 25. The reflective pixel electrode 23contacts the expansion source electrode 33 in the contact holes 29, 30,and is formed on the organic insulating film 26 and coated with thealignment film 31.

[0047] The organic insulating film 26 has an upper surface in which afirst molding undulation gradually depressed toward the vicinity of amiddle from an outer edge in a range of each pixel area PX and a secondmolding undulation rising in a plurality of positions in the range ofthe pixel area PX are superimposed. That is, the first moldingundulation is a gradual inclined surface, and is constituted of a convexportion 26 a arranged along the outer edge in the range of the pixelarea PX, and a concave portion 26 b surrounded by the convex portion 26a. The second molding undulation is constituted of a plurality ofhemispheric convex portions 26 c arranged at random in the range of thepixel area PX, and concave portions 26 d surrounding these convexportions 26 c.

[0048] The reflective pixel electrode 23 functions as a reflective platefor scattering a light incident from the counter substrate 11 via theliquid crystal layer 12 at a high reflectance, contains materials suchas silver, aluminum, and an alloy of these, and is formed in apredetermined thickness along the upper surface of the organicinsulating film 26. Therefore, the reflective pixel electrode 23 isformed on the upper surface of the organic insulating film 26, and isdefined to have a reflective surface in which a first undulation formedby disposing the gradual inclined surface in the range of the pixel areaPX and a second undulation formed by disposing a plurality of mainscattering portions in the range of the pixel area PX are superimposed.

[0049] That is, the first undulation of the reflective pixel electrode23 is constituted of a concave portion 23 b corresponding to the concaveportion 26 b of the organic insulating film 26, and a convex portion 23a corresponding to the convex portion 26 a of the organic insulatingfilm 26. The second undulation of the reflective pixel electrode 23 isconstituted of a convex portion 23 c corresponding to the convex portion26 c of the organic insulating film 26, and a concave portion 23 dcorresponding to the concave portion 26 d of the organic insulating film26. The gradual inclined surface of the first undulation is obtained asa combination of the convex portion 23 a and concave portion 23 b. Themain scattering portion of the second undulation is obtained as therandomly disposed convex portion 23 c or concave portion 23 d In FIG. 1,H1 indicates a difference of elevation of the first undulation as aheight of the convex portion 23 a or a depth of the concave portion 23b, and H2 indicates a difference of elevation of the second undulationas a height of the convex portion 23 c or a depth of the concave portion23 d.

[0050] Manufacturing steps of the aforementioned reflective liquidcrystal display device will next be described.

[0051]FIGS. 4A to 4H show the manufacturing steps of the array substrate10. In manufacturing of the array substrate 10, first the semiconductorlayer 16 is formed on the insulating substrate 13 of a glass plate,quartz plate, or the like. The semiconductor layer 16 is formed bydepositing, for example, amorphous silicon on the insulating substrate13 in a thickness of about 50 nm by a CVD process, and patterning thislayer by a photo-etching process.

[0052] Subsequently, the gate insulating film 17 is formed by depositingSiOx on the semiconductor layer 16 and insulating substrate 13 in athickness of the order of 100 nm to 150 nm by the CVD process.

[0053] Subsequently, the gate electrode 18 and scanning line 15 areintegrally formed by depositing a single metal such as Ta, Cr, Al, Mo,W, and Cu, or a deposited or alloy film of the metals on the gateinsulating film 17 in a thickness of the order of 200 nm to 400 nm, andpatterning the film by the photo-etching process. Thereafter, animpurity such as phosphorus is injected into the semiconductor layer 16by an ion injecting or doping process using the gate electrode 18 as amask. Here, phosphorus is accelerated, for example, at an accelerationvoltage of 80 keV in an atmosphere of PH₃/H₂, and injected at a dosageof 5×10¹⁵ atoms/cm², that is, at a high concentration. The impurityinjected area is activated by annealing the semiconductor layer 16, andconstitutes a source and drain of the thin film transistor 24.

[0054] In the step shown in FIG. 4A, the interlayer insulating film 32is formed by using, for example, a PECVD process to deposit SiOx on thegate electrode 18, scanning line 15, and gate oxide film 17 in athickness of the order of 500 nm to 700 nm. Thereafter, the interlayerinsulating film 32 is patterned by the photo-etching process so that thesource and drain of the semiconductor layer 16 are exposed, and therebythe contact holes 21 and 22 are formed.

[0055] In the step shown in FIG. 4B, the single metal such as Ta, Cr,Al, Mo, W, and Cu, or the laminated or alloy film of the metals isdeposited on the interlayer insulating film 32 in a thickness of theorder of 500 nm to 700 nm, and patterned into a predetermined shape bythe photo-etching process, so that wirings such as the signal line 14,source electrode 19, expansion source electrode 33, and scanning line 15are formed.

[0056] In the step shown in FIG. 4C, the protective insulating film 25is formed by depositing SiNx on these wirings and interlayer insulatingfilm 32 by the PECVD process. Thereafter, the contact hole 29 is formedby patterning the protective insulating film 25 by the photo-etchingprocess.

[0057] In the step shown in FIG. 4D, the organic insulating film 26 isformed by applying a positive photosensitive resin on the protectiveinsulating film 25 in a thickness of the order of 1 μm to 4 μm by a spincoating process or the like, and further pre-baking the whole arraysubstrate 10. When a viscosity and spin rotation number of thephotosensitive resin are optimized, the first molding undulation of theconvex portion 26 a and concave portion 26 b can be formed in the pixelarea PX surrounded by the two adjacent signal lines 14 and two adjacentscanning lines 15. Concretely, the difference of elevation of the orderof 0.1 μm to 0.5 μm is generated in the upper surface of the organicinsulating film 26 depending upon the thickness of the wiring materialssuch as the scanning line 15 and signal line 14. The convex portion 26 ais disposed in the outer edge of each pixel area PX, that is, in aboundary with the adjacent pixel area, and the concave portion 26 b isdisposed to be surrounded by the convex portion 26 a. Therefore, adimension D1 of the concave portion 26 b substantially agrees with apixel pitch usually of the order of 20 μm to 400 μm.

[0058] In the step shown in FIG. 4E, a first photo mask is used topartially expose the organic insulating film 26 in a range correspondingto the contact hole 29. An opening is made in the organic insulatingfilm 26 in order to form the contact hole 30 in which the expansionsource electrode 33 is exposed. Therefore, a exposure i is preferably ofthe order of 200 mJ to 1000 mJ.

[0059] Subsequently, a second photo mask 34 is used to expose theorganic insulating film 26 in the range of the pixel area PX. The secondphoto mask has a circular shielding portion disposed at random such thatthe portion is prevented from overlapping with the signal line 14 andscanning line 15. Here, a diameter of the shielding portion is set to beof the order of 2 μm to 20 μm, which is smaller than the dimension D1 ofthe concave portion 26 b, and the exposure is set to a range of 10 mJ to200 mJ. The undulation of the organic insulating film 26, that is, aconcave/convex shape and density can be controlled in accordance with anopening shape, the opening density of the photo mask 34, exposure, andthe like.

[0060] In the step shown in FIG. 4F, the organic insulating film 26 isdeveloped in order to remove the aforementioned exposed portion, andthereby a plurality of convex portions 26 c′ and concave portions 26 d′are formed in the organic insulating film 26 together with the contacthole 30. Additionally, in the exposure using the second photo mask 34,the exposure is in the range of 10 to 200 mJ. Therefore, a bottom of theconcave portion 26 d′ does not reach the protective insulating film 25as a substrate of the organic insulating film 26, and remains in thevicinity of the upper surface of the organic insulating film 26.

[0061] In the step shown in FIG. 4G, a heating treatment of the arraysubstrate 10 is performed. This changes the convex portion 26 c′ andconcave portion 26 d′ of the organic insulating film 26 to the chamferedsmoothly hemispheric convex portion 26 c and the concave portion 26 dsurrounding the convex portion 26 c, and the second molding undulationis formed. A diameter D2 of the convex portion 26 c is set to be smallerthan the dimension D1 of the concave portion 26 b in accordance with thediameter of the shielding portion.

[0062] In the step shown in FIG. 4H, a metal film of Al, Ni, Cr, Ag orthe like is deposited on the organic insulating film 26 in a thicknessof about 100 nm by a sputtering process, and patterned in apredetermined shape in the photo-etching process, and thereby thereflective pixel electrode 23 is formed.

[0063] In the manufacturing of the counter substrate 11, the glassplate, quartz plate, or the like is used as the insulating substrate 36permeable to light, and the coloring layer 37 with a pigment, and thelike dispersed therein is formed on the insulating substrate 36. Thetransparent counter electrode 38 is formed by depositing, for example,ITO on the coloring layer 37 by the sputtering process.

[0064] The array substrate 10 and counter substrate 11 are integrallyformed after the alignment films 31 and 39 are formed. The alignmentfilm 31 is formed by applying low-temperature cure type polyimide byprinting so that the reflective pixel electrode 23 and organicinsulating film 26 are coated, and performing a rubbing treatment.Moreover, the alignment film 39 is formed by applying low-temperaturecure type polyimide by printing so that the transparent counterelectrode 38 is coated, and performing a rubbing treatment.

[0065] The array substrate 10 and counter substrate 11 are obtained asdescribed above, and disposed opposite to each other, while thealignment films 31 and 39 are disposed inside. These substrates areattached to each other via a peripheral edge seal material at apredetermined interval. The liquid crystal layer 12 is obtained byforming a liquid crystal injected space surrounded by the peripheraledge seal material into a cell between the array substrate 10 and thecounter substrate 11, and injecting and sealing a liquid crystalcomposition such as a nematic liquid crystal into the cell. Thepolarization plate 40 is attached to the transparent insulatingsubstrate 36 on the side opposite to the coloring layer 37. Thereflective liquid crystal display device is completed as describedabove.

[0066] In the liquid crystal display device according to the firstembodiment, the reflective pixel electrode 23 constitutes the reflectiveplate, and the reflective surface has a state in which the firstundulation having the difference of elevation H1 and the secondundulation having the difference of elevation H2 are superimposed. Thefirst undulation is constituted of the convex portion 23 a disposedalong the outer edge in the range of the pixel area PX, and the concaveportion 23 b surrounded by the convex portion 23 a. The secondundulation is constituted of the plurality of hemispheric convexportions 23 c arranged at random in the range of the pixel area PX, andthe concave portions 23 d surrounding these convex portions 23 c.

[0067] That is, the first undulation is gradually depressed toward thevicinity of the middle from the outer edge in the range of each pixelarea PX, and is is formed by disposing the gradual inclined surface ineach pixel area PX. Moreover, the second undulation rises in theplurality of positions in the range of the pixel area PX, and is formedby disposing the plurality of main scattering portions in each pixelarea PX.

[0068] A reflected light on the reflective surface is scattered by aninclination angle obtained by superimposing an inclination angleobtained by the second undulation upon the inclination angle obtained bythe first undulation. Therefore, even when the inclination angleobtained by the second undulation is small, an optimum reflectionproperty can be obtained. On the other hand, the difference of elevationin a micro range can be set to a value sufficiently smaller than aconventional value, such as H2. Therefore, a liquid crystal alignmentdefect attributed to the difference of elevation can be prevented. As aresult, the reflective liquid crystal display device can display ahigh-quality image having a broad angle of field of view and highcontrast.

[0069] In the first embodiment, the second undulation is disposed in aposition excluding a space between the reflective pixel electrodes 23.This does not substantially cause deterioration of a reflection propertyof the reflective surface, and additionally the second moldingundulation on the side of the organic insulating film 26 can be obviatedin the range of the space. Therefore, a patterning defect is notgenerated during patterning of the metal film deposited using theorganic insulating film 26 as the substrate in the step of forming thereflective pixel electrode 23, and a point defect by a short-circuitbetween the pixel electrodes 23 can be reduced. Moreover, the secondmolding undulation is disposed so that the undulation is prevented fromoverlapping with the scanning line 15 and signal line 14. Therefore, aparasitic capacity between the scanning line 15 and the pixel electrode23 and between the signal line 14 and the pixel electrode 23 can bereduced. Therefore, a display quality can be prevented from beingdeteriorated by cross talk, or the like.

[0070] The reflective liquid crystal display device according to asecond embodiment of the present invention will next be described. FIG.5 shows the plane structure in the vicinity of the pixel of thereflective liquid crystal display device, and FIG. 6 shows a sectionalstructure taken along line VI-VI shown in FIG. 5. The liquid crystaldisplay device is constituted similarly as the first embodiment exceptthe following structure. Therefore, in FIGS. 5 and 6, a part similar tothat of the first embodiment is denoted with the same reference numeral,and the description thereof is omitted.

[0071] As shown in FIG. 5, in this liquid crystal display device, theprotective insulating film 25 is selectively removed so that theinterlayer insulating film 32 is exposed and a plurality of islandportions 50 are left in an area corresponding to the reflective pixelelectrode 23, and the organic insulating film 26 is formed using theprotective insulating film 25 and interlayer insulating film 32 assubstrates. This island portion 50 is disposed inside the outer edge ofeach pixel area. In this case, the first molding undulation is obtainedin the upper surface of the organic insulating film 26 depending uponthe aforementioned constitution, and the reflective pixel electrode 23is formed along the upper surface.

[0072] Thereby, the inclination angle of the first undulation of thereflective pixel electrode 23 is formed depending upon the thickness ofthe plurality of island portions. Moreover, the reflective undulation ofthe reflective pixel electrode 23 is obtained in which the plurality ofmain scattering portions, that is, convex portions 23 c are disposed inthe gradual inclined surface as shown in FIG. 6. The reflective pixelelectrode 23 is formed along the upper surface as shown in FIG. 6.

[0073] Similarly as the first embodiment, in the reflective liquidcrystal display device of the second embodiment, the alignment defect ofliquid crystal can be prevented without deteriorating a satisfactoryoptical reflection property. Moreover, an interval of the islandportions 50 can arbitrarily be changed. Therefore, even with a largepixel pitch, a situation in which the optical reflection property cannotbe optimized cannot easily be induced. Furthermore, since these islands50 are arranged at random, light interference attributed to regularityof a light scattering pattern is prevented and coloring of the reflectedlight can be reduced.

[0074] The reflective liquid crystal display device according to a thirdembodiment of the present invention will next be described. FIG. 7 showsthe plane structure in the vicinity of the pixel of the reflectiveliquid crystal display device, and FIG. 8 shows a sectional structuretaken along line VIII-VIII shown in FIG. 7. The liquid crystal displaydevice is constituted similarly as the first embodiment except thefollowing structure. Therefore, in FIGS. 7 and 8, the part similar tothat of the first embodiment is denoted with the same reference numeral,and the description thereof is omitted.

[0075] In the liquid crystal display device, as shown in FIG. 7, eachscanning line 15 is disposed to cross a middle of the reflective pixelelectrode 23 below the corresponding reflective pixel electrode 23. Whenthe scanning line 15 is coated with the successively formed interlayerinsulating film 32, protective insulating film 25, and organicinsulating film 26, the first molding undulation is obtained in theupper surface of the organic insulating film 26 depending upon theaforementioned constitution, and the reflective pixel electrode 23 isformed along the upper surface.

[0076] Thereby, the inclination angle of the first undulation of thereflective pixel electrode 23 is set depending upon the thickness of thescanning line 15. Moreover, the reflective surface of the reflectivepixel electrode 23 is obtained in which the plurality of main scatteringportions, that is, convex portions 23 c are formed on the gradualinclined surface as shown in FIG. 8.

[0077] In the reflective liquid crystal display device of the thirdembodiment, similarly as the first embodiment, the alignment defect ofliquid crystal can be prevented without deteriorating the satisfactoryoptical reflection property. Furthermore, since the scanning line 15 isnot disposed between the reflective pixel electrodes 23, the lightreflected by the surface of the scanning line 15 is suppressed, and thehigh-quality image having a high contrast can be displayed.

[0078] The reflective liquid crystal display device according to afourth embodiment of the present invention will next be described. FIG.9 shows manufacturing steps of the reflective liquid crystal displaydevice. The liquid crystal display device is constituted similarly asthe first embodiment except the following structure. Therefore, in FIG.9, the part similar to that of the first embodiment is denoted with thesame reference numeral, and the description thereof is omitted.

[0079] In the manufacturing of the array substrate 10, the glass plate,quartz plate, or the like is used as the insulating substrate 13, andthe semiconductor layer 16 is formed by depositing, for example,amorphous silicon on the insulating substrate 13 in a thickness of about50 nm by the CVD process, and patterning this layer by the photo-etchingprocess.

[0080] Subsequently, the gate insulating film 17 is formed by depositingSiox on the semiconductor layer 16 and insulating substrate 13 in athickness of the order of 100 nm to 150 nm by the CVD process.

[0081] Subsequently, the gate electrode 18 and scanning line 15 areintegrally formed by depositing the single metal such as Ta, Cr, Al, Mo,W and Cu, or the deposited or alloy film of the metals on the gateinsulating film 17 in a thickness of the order of 200 nm to 400 nm, andpatterning the film by the photo-etching process. Thereafter, theimpurity such as phosphorus is injected into the semiconductor layer 16by the ion injecting or doping process using the gate electrode 18 asthe mask. Here, phosphorus is accelerated, for example, at anacceleration voltage of 80 keV in an atmosphere of PH₃/H₂, and injectedat a dosage of 5×10¹⁵ atoms/cm², that is, at a high concentration. Theimpurity injected area is activated by annealing the semiconductor layer16, and constitutes the source and drain of the thin film transistor 24.

[0082] Subsequently, the array substrate 10 is successively treated inthe steps shown in FIGS. 9A to 9D. The steps shown in FIGS. 9A to 9D aresimilar to the steps shown in FIGS. 4A to 4D described in the firstembodiment. Therefore, the difference of elevation of the order of 0.1μm to 0.5 μm is generated in the upper surface of the organic insulatingfilm 26 depending upon the thickness of the wiring materials such as thescanning line 15 and signal line 14. The convex portion 26 a is disposedin the outer edge of each pixel area PX, that is, in the boundary withthe adjacent pixel area, and the concave portion 26 b is disposed to besurrounded by the convex portion 26 a. Therefore, the dimension D1 ofthe concave portion 26 b substantially agrees with the pixel pitchusually of the order of 20 μm to 400 μm.

[0083] In the step shown in FIG. 9E, an organic insulating film 63 isformed by applying a photosensitive resin on the organic insulating film26 in a thickness of 0.6 μm by the spin coating process, and pre-bakingthe array substrate 10.

[0084] In the step shown in FIG. 9F, a photo mask 64 is used to exposethe organic insulating film 63 in the range of the pixel area PX. Themask has a circular transmitting portion disposed at random such thatthe portion is prevented from overlapping with the signal line 14 andscanning line 15. Here, a diameter of the transmitting portion is set tobe of the order of 2 μm to 20 μm, which is smaller than the dimension D1of the concave portion 26 b, and the exposure is set to a range of 50 mJto 4000 mJ. The undulation of the organic insulating film 63, that is,the concave/convex shape and density can be controlled in accordancewith the opening shape, the opening density of the photo mask 64,exposure, and the like.

[0085] In the step shown in FIG. 9G, the organic insulating film 63 isdeveloped in order to remove the aforementioned exposed portion from theorganic insulating film 26, and thereby a plurality of micro circularconcave portions 63 b′ and a convex portion 63 a′ surrounding theseconcave portions 63 b′ are formed.

[0086] In the step shown in FIG. 9H, the heating treatment of the arraysubstrate 10 is performed. This changes the concave portion 63 b′ andconvex portion 63 a′ of the organic insulating film 63 to the chamferedsmooth concave portion 63 b and convex portion 63 a surrounding theconcave portion 63 b.

[0087] In the step shown in FIG. 9I, an organic insulating film 67 isformed by applying the photosensitive resin similar to the resin used informing the organic insulating film 63 on the organic insulating film 26in a thickness of 0.3 μm by the spin coating process so that the concaveportion 63 b and convex portion 63 a are coated, and pre-baking thearray substrate 10. Thereby, the second molding undulation is obtainedin the organic insulating film 67. The second molding undulation isconstituted by concave portions 67 b and convex portions 67 asurrounding these concave portions 67 b.

[0088] In the step shown in FIG. 9J, a metal film of Al, Ni, Cr, Ag orthe like is deposited on the organic insulating film 67 in a thicknessof about 100 nm by the sputtering process, and patterned in thepredetermined shape by the photo-etching process, and thereby thereflective pixel electrode 23 is formed.

[0089] In the reflective liquid crystal display device of the fourthembodiment, the reflective pixel electrode 23 constitutes the reflectiveplate, and the reflective surface has a state in which the firstundulation having the difference of elevation H1 and second undulationhaving the difference of elevation H2 are superimposed. The firstundulation is constituted of the convex portions 23 a arranged along theouter edge in the range of each pixel area PX, and the concave portion23 b surrounded by the convex portion 23 a. The second undulation isconstituted of a plurality of hemispheric concave portions 23 e arrangedat random in the range of each pixel area PX, and convex portions 23 fsurrounding these concave portions 23 e. That is, the first undulationis gradually depressed toward the vicinity of the middle from the outeredge in the range of each pixel area PX, and is formed by disposing thegradual inclined surface in the range of each pixel area PX. Moreover,the second undulation is depressed in the plurality of positions in therange of the pixel area PX, and is formed by disposing the plurality ofmain scattering portions in the range of each pixel area.

[0090] Even in this constitution, similarly as the first embodiment, thealignment defect of the liquid crystal can be prevented withoutdeteriorating the satisfactory optical reflection property.

[0091] The liquid crystal display device according to a fifth embodimentof the present invention will next be described.

[0092]FIG. 11 shows the sectional structure in the vicinity of the pixelof a semi-transmission type liquid crystal display device, FIG. 12 showsthe plane structure in the vicinity of the pixel of thesemi-transmission type liquid crystal display device, and FIG. 13 showsa sectional structure taken along line A-B shown in FIG. 12. Thesemi-transmission type liquid crystal display device includes the arraysubstrate 10, counter substrate 11, and liquid crystal layer 12 heldbetween these substrates 10 and 11. The semi-transmission type liquidcrystal display device has a reflection function formed by thereflective plate for scattering the incident light via the countersubstrate 11 and liquid crystal layer 12, and also has a transmissionfunction for transmitting the incident light via the array substrate 10.

[0093] The array substrate 10 includes the insulating substrate 13, theplurality of reflective pixel electrodes 23 arranged in the matrix form,the plurality of signal lines 14 arranged along the row of thesereflective pixel electrodes 23, the plurality of scanning lines 15arranged along the line of these reflective pixel electrodes 23, theplurality of thin film transistors for pixels (TFT) 24 arranged as theswitching elements in the vicinity of intersection positions of thecorresponding scanning line 15 and signal line 14, and the alignmentfilm 31 with which the plurality of reflective pixel electrodes 23 arecoated.

[0094] The counter substrate 11 includes the insulating substrate 36having permeability to light, the coloring layer 37 forming the colorfilter with which the insulating substrate 36 is coated, the transparentcounter electrode 38 with which the coloring layer 37 is coated, and thealignment film 39 with which the counter electrode 38 is coated.Moreover, the polarization plate 40 is attached to the transparentinsulating substrate 36 on the side opposite to the coloring layer 37.

[0095] The liquid crystal layer 12 is divided into the plurality ofpixel areas PX for the plurality of reflective pixel electrodes 23. Eachpixel area PX is disposed between two adjacent scanning lines 15 and twoadjacent signal lines 14. Each thin film transistor 24 becomesconductive in response to the scanning pulse supplied from thecorresponding scanning line 15, and supplies the potential of thecorresponding signal line 14 to the corresponding reflective pixelelectrode 23. Each reflective pixel electrode 23 applies the potentialof the corresponding signal line 14 as the pixel potential to thecorresponding pixel area PX of the liquid crystal layer 12, and controlsthe transmittance of the pixel area PX based on the difference betweenthe pixel potential and the potential of the counter electrode 38.

[0096] In the array substrate 10, each TFT 24 includes the semiconductorlayer 16 of amorphous silicon or polysilicon, the gate electrode 18formed above the semiconductor layer 16 in the insulated manner andconnected to the corresponding scanning line 15, and the source anddrain electrodes 19, 20 which contact the source area 16S and drain area16D of the semiconductor layer 16 via the contact holes 21, 22 on theopposite sides of the gate electrode 18 and which are connected to thecorresponding reflective pixel electrode 23 and corresponding signalline 14, respectively.

[0097] The semiconductor layer 16 is formed on the insulating substrate13, and coated with the gate insulating film 17 together with theinsulating substrate 13. The gate electrode 18 is insulated from thesemiconductor layer 16 by the gate insulating film 17, and integrallyformed with the corresponding scanning line 15 on the gate insulatingfilm 17. The gate electrode 18 and scanning line 15 as well as the gateinsulating film 17 are coated with the interlayer insulating film 32.

[0098] The contact holes 21, 22 are formed in the interlayer insulatingfilm 32 and gate insulating film 17 so that the source area 16S anddrain area 16D formed in the semiconductor layer 16 are exposed on theopposite sides of the gate electrode 18. The source electrode 19 anddrain electrode 20 are in contact with the source area 16S and drainarea 16D of the semiconductor layer 16 in these contact holes 21, 22,respectively, and formed on the interlayer insulating film 32.

[0099] The source electrode 19 is integrally formed with the expansionsource electrode 33 on the interlayer insulating film 32. The drainelectrode 20 is integrally formed with the corresponding signal line 14on the interlayer insulating film 32. The source electrode 19, expansionsource electrode 33, drain electrode 20, and signal line 14, togetherwith the interlayer insulating film 32, are coated with the protectiveinsulating film 25.

[0100] The protective insulating film 25 has the contact hole 29 inwhich the expansion source electrode 33 is partially exposed, and iscoated with the organic insulating film 26. The organic insulating film26 has the contact hole 30 in which the expansion source electrode 33 ispartially exposed, and the contact hole 30 is formed in the contact hole29 of the protective insulating film 25. The reflective pixel electrode23 contacts the expansion source electrode 33 in the contact holes 29,30, and is formed on the organic insulating film 26 and coated with thealignment film 31.

[0101] The organic insulating film 26 has the upper surface in which thefirst molding undulation gradually depressed toward the vicinity of themiddle from the outer edge in the range of each pixel area PX and thesecond molding undulation rising in the plurality of positions in therange of the pixel area PX are superimposed. That is, the first moldingundulation is the gradual inclined surface, and is constituted of theconvex portion 26 a arranged along the outer edge in the range of thepixel area PX, and the concave portion 26 b surrounded by the convexportion 26 a. The second molding undulation is constituted of theplurality of hemispheric convex portions 26 c arranged at random in therange of the pixel area PX, and concave portions 26 d surrounding theseconvex portions 26 c.

[0102] The reflective pixel electrode 23 functions as the reflectiveplate for scattering the light incident from the counter substrate 11via the liquid crystal layer 12 at the high reflectance, containsmaterials such as silver, aluminum, and an alloy of these, and is formedin the predetermined thickness along the upper surface of the organicinsulating film 26. Therefore, the reflective pixel electrode 23 isformed on the upper surface of the organic insulating film 26, and isdefined to have the reflective surface in which the first undulationformed by disposing the gradual inclined surface in the range of thepixel area PX and the second undulation formed by disposing theplurality of main scattering portions in the range of the pixel area PXare superimposed.

[0103] Moreover, the reflective pixel electrode 23 has a hole fortransmission 23 e which can pass the incident light via the arraysubstrate 10.

[0104] That is, the first undulation of the reflective pixel electrode23 is constituted of the concave portion 23 b corresponding to theconcave portion 26 b of the organic insulating film 26, and the convexportion 23 a corresponding to the convex portion 26 a of the organicinsulating film 26. The second undulation of the reflective pixelelectrode 23 is constituted of the convex portion 23 c corresponding tothe convex portion 26 c of the organic insulating film 26, and theconcave portion 23 d corresponding to the concave portion 26 d of theorganic insulating film 26. The gradual inclined surface of the firstundulation is obtained as the combination of the convex portion 23 a andconcave portion 23 b. The main scattering portion of the secondundulation is obtained as the convex portion 23 c. In FIG. 11, H1indicates the difference of elevation of the first undulation as theheight of the convex portion 23 a or the depth of the concave portion 23b, and H2 indicates the difference of elevation of the second undulationas the height of the convex portion 23 c or the depth of the concaveportion 23 d.

[0105] Manufacturing steps of the aforementioned reflective liquidcrystal display device will next be described.

[0106]FIGS. 14A to 14H show the manufacturing steps of the arraysubstrate 10. In the manufacturing of the array substrate 10, the glassplate, quartz plate, or the like is used as the insulating substrate 13.The semiconductor layer 16 constituting a channel layer of the pixel TFT24 is formed by depositing, for example, amorphous silicon on theinsulating substrate 13 in a thickness of about 50 nm by the CVDprocess, and patterning this layer by the photo-etching process.

[0107] Subsequently, the gate insulating film 17 is formed by depositingSiOx on the semiconductor layer 16 and insulating substrate 13 in athickness of the order of 100 nm to 150 nm by the CVD process.

[0108] Subsequently, the gate electrode 18 and scanning line 15 areintegrally formed by depositing the single metal such as Ta, Cr, Al, Mo,W, and Cu, or the deposited or alloy film of the metals on the gateinsulating film 17 in a thickness of the order of 200 nm to 400 nm, andpatterning the film by the photo-etching process. Thereafter, theimpurity such as phosphorus is injected into the semiconductor layer 16by the ion injecting or doping process using the gate electrode 18 asthe mask. Here, phosphorus is accelerated, for example, at anacceleration voltage of 80 keV in an atmosphere of PH₃/H₂, and injectedat a dosage of 5×10¹⁵ atoms/cm², that is, at the high concentration. Theimpurity injected area is activated by annealing the semiconductor layer16, and constitutes the source area 16S and drain 16D of the thin filmtransistor 24.

[0109] In the step shown in FIG. 14A, the interlayer insulating film 32is formed by using, for example, the PECVD process to deposit SiOx onthe gate electrode 18, scanning line 15, and gate oxide film 17 in athickness of the order of 500 nm to 700 nm. The interlayer insulatingfilm 32 is patterned by the photo-etching process so that the sourcearea 16S and drain 16D of the semiconductor layer 16 are exposed, andthereby the contact holes 21 and 22 are formed.

[0110] In the step shown in FIG. 14B, the single metal such as Ta, Cr,Al, Mo, W, and Cu, or the laminated or alloy film of the metals isdeposited on the interlayer insulating film 32 in a thickness of theorder of 500 nm to 700 nm, and patterned into the predetermined shape bythe photo-etching process, so that wirings such as the signal line 14,source electrode 19, drain electrode 20, and expansion source electrode33 are formed.

[0111] In the step shown in FIG. 14C, the transparent protectiveinsulating film 25 is formed by depositing SiNx on these wirings andinterlayer insulating film 32 by the PECVD process, and the contact hole29 is formed by patterning the protective insulating film 25 by thephoto-etching process.

[0112] In the step shown in FIG. 14D, the organic insulating film 26 isformed by applying the positive photosensitive resin on the protectiveinsulating film 25 in a thickness of the order of 1 μm to 4 μm by thespin coating process or the like, and further pre-baking the whole arraysubstrate 10. When the viscosity and spin rotation number of thephotosensitive resin are optimized, the first molding undulation of theconvex portion 26 a and concave portion 26 b is formed in the range ofthe pixel area PX surrounded by the two adjacent signal lines 14 and twoadjacent scanning lines 15. Concretely, the difference of elevation ofthe order of 0.1 μm to 0.5 μm is generated in the upper surface of theorganic insulating film 26 depending upon the thickness of the wiringmaterials such as the scanning line 15 and signal line 14. The convexportion 26 a is disposed in the outer edge of each pixel area PX, thatis, in the boundary with the adjacent pixel area, and the concaveportion 26 b is disposed to be surrounded by the convex portion 26 a.Therefore, the dimension Dl of the concave portion 26 b substantiallyagrees with the pixel pitch usually of the order of 20 μm to 400 μm.

[0113] In the step shown in FIG. 14E, the first photo mask is used topartially expose the organic insulating film 26 in the rangecorresponding to the contact hole 29. The opening is made in the organicinsulating film 26 in order to form the contact hole 30 in which theexpansion source electrode 33 is exposed. Therefore, the exposure i ispreferably of the order of 200 mJ to 1000 mJ.

[0114] Subsequently, the second photo mask 34 is used to expose theorganic insulating film 26 in the range of the pixel area PX. The secondphoto mask has a circular shielding portion disposed at random such thatthe portion is prevented from overlapping with the signal line 14 andscanning line 15. Here, the diameter of the shielding portion is set tobe of the order of 2 μm to 20 μm, which is smaller than the dimension D1of the concave portion 26 b, and the luminous exposure is set to a rangeof 10 mJ to 200 mJ. The undulation of the organic insulating film 26,that is, the concave/convex shape and density can be controlled inaccordance with the opening shape, the opening density of the photo mask34, luminous exposure, and the like.

[0115] In the step shown in FIG. 14F, the organic insulating film 26 isdeveloped in order to remove the aforementioned exposed portion, andthereby the plurality of convex portions 26 c′ and concave portions 26d′ are formed in the organic insulating film 26 together with thecontact hole 30. Additionally, in the exposure using the second photomask 34, the exposure is in the range of 10 to 200 mJ. Therefore, thebottom of the concave portion 26 d′ does not reach the protectiveinsulating film 25 as the substrate of the organic insulating film 26,and remains in the vicinity of the upper surface of the organicinsulating film 26.

[0116] In the step shown in FIG. 14G, the heating treatment of the arraysubstrate 10 is performed. This changes the convex portion 26 c′ andconcave portion 26 d′ of the organic insulating film 26 to the chamferedsmoothly hemispheric convex portion 26 c and the concave portion 26 dsurrounding the convex portion 26 c, and the second molding undulationis formed. The diameter D2 of the convex portion 26 c is set to besmaller than the dimension D1 of the concave portion 26 b in accordancewith the diameter of the shielding portion.

[0117] In the step shown in FIG. 14H, the metal film of Al, Ni, Cr, Agor the like is deposited on the organic insulating film 26 in athickness of about 100 nm by the sputtering process, and patterned intothe predetermined shape by the photo-etching process, and thereby thereflective pixel electrode 23 is formed. In this case, the hole fortransmission 23 e is simultaneously formed in a part of the reflectivepixel electrode 23.

[0118] In the manufacturing of the counter substrate 11, the glassplate, quartz plate, or the like is used as the insulating substrate 36permeable to light, and the coloring layer 37 with the pigment, and thelike dispersed therein is formed on the insulating substrate 36. Thetransparent counter electrode 38 is formed by depositing, for example,ITO on the coloring layer 37 by the sputtering process.

[0119] The array substrate 10 and counter substrate 11 are integrallyformed after the alignment films 31 and 39 are formed. The alignmentfilm 31 is formed by applying low-temperature cure type polyimide byprinting so that the reflective pixel electrode 23 and organicinsulating film 26 are coated, and performing the rubbing treatment.Moreover, the alignment film 39 is formed by applying low-temperaturecure type polyimide by printing so that the transparent counterelectrode 38 is coated, and performing the rubbing treatment.

[0120] The array substrate 10 and counter substrate 11 are obtained asdescribed above, and disposed opposite to each other, while thealignment films 31 and 39 are disposed inside. These substrates areattached to each other via the peripheral edge seal material at thepredetermined interval. The liquid crystal layer 12 is obtained byforming the liquid crystal injected space surrounded by the peripheraledge seal material into the cell between the array substrate 10 and thecounter substrate 11, and injecting and sealing the liquid crystalcomposition such as the nematic liquid crystal into the cell. Thepolarization plate 40 is attached to the transparent insulatingsubstrate 36 on the side opposite to the coloring layer 37, while theliquid crystal layer 12 is held between the array substrate 10 and thecounter substrate 11. The semi-transmission type liquid crystal displaydevice is completed as described above.

[0121] In the semi-transmission liquid crystal display device accordingto the fifth embodiment, the reflective pixel electrode 23 constitutesthe reflective plate, and the reflective surface has a state in whichthe first undulation having the difference of elevation H1 and thesecond undulation having the difference of elevation H2 aresuperimposed. The first undulation is constituted of the convex portion23 a disposed along the outer edge in the range of the pixel area PX,and the concave portion 23 b surrounded by the convex portion 23 a. Thesecond undulation is constituted of the plurality of hemispheric convexportions 23 c arranged at random in the range of the pixel area PX, andthe concave portion 23 d surrounding these convex portions 23 c.

[0122] That is, the first undulation is gradually depressed toward thevicinity of the middle from the outer edge in the range of each pixelarea PX, and is formed by disposing the gradual inclined surface in eachpixel area PX. Moreover, the second undulation rises in the plurality ofpositions in the range of the pixel area PX, and is formed by disposingthe plurality of main scattering portions in each pixel area PX.

[0123] A reflected light on the reflective surface is scattered by theinclination angle obtained by superimposing the inclination angleobtained by the second undulation upon the inclination angle obtained bythe first undulation. Therefore, even when the inclination angleobtained by the second undulation is small, the optimum reflectionproperty can be obtained. On the other hand, the difference of elevationin the micro range can be set to the value sufficiently smaller than theconventional value, such as H2. Therefore, the liquid crystal alignmentdefect attributed to the difference of elevation can be prevented. As aresult, the semi-transmission type liquid crystal display device candisplay the high-quality image having the broad angle of field of viewand high contrast.

[0124] In the fifth embodiment, the second undulation is not disposed inthe space between the reflective pixel electrodes 23. This does notsubstantially cause deterioration of the reflection property of thereflective surface, and additionally the second molding undulation onthe side of the organic insulating film 26 can be obviated in the rangeof the space. Therefore, the patterning defect is not generated duringpatterning of the metal film deposited using the organic insulating film26 as the substrate in the step of forming the reflective pixelelectrode 23, and the point defect by the short-circuit between thepixel electrodes 23 can be reduced. Moreover, the second moldingundulation is disposed so that the undulation is prevented fromoverlapping with the scanning line 15 and signal line 14. Therefore, theparasitic capacity between the scanning line 15 and the pixel electrode23 and between the signal line 14 and the pixel electrode 23 can bereduced. Therefore, the display quality can be prevented from beingdeteriorated by cross talk, or the like.

[0125] The semi-transmission type liquid crystal display deviceaccording to a sixth embodiment of the present invention will next bedescribed.

[0126]FIG. 15 shows the sectional structure of the semi-transmissiontype liquid crystal display device. The semi-transmission type liquidcrystal display device is constituted similarly as the fifth embodimentexcluding the following structure. Therefore, in FIG. 15, a part similarto that of the fifth embodiment is denoted with the same referencenumeral, and the description thereof is omitted.

[0127] As shown in FIG. 15, in this semi-transmission type liquidcrystal display device, a transparent pixel electrode 23 f formed by atransparent conductive member such as ITO is disposed in an areacorresponding to the hole for transmission 23 e of the reflective pixelelectrode 23. The organic insulating film 26 having concave/convex isdisposed as the substrate in the area corresponding to the hole fortransmission 23 e, and the transparent pixel electrode 23 f is disposedon the organic insulating film 26.

[0128] Moreover, the semi-transmission type liquid crystal displaydevice includes a back light unit 42 for lighting from a side of thearray substrate 10. Furthermore, the semi-transmission type liquidcrystal display device includes a polarization plate 41 on the surfaceof the array substrate 10 disposed opposite to the back light unit 42.For example, the polarization plate 41 is disposed such that apolarization surface crosses at right angles to the polarization plate40 disposed on the counter substrate 11.

[0129] When this semi-transmission type liquid crystal display device isutilized as a reflective type, similarly as the aforementionedembodiments, the external light incident via the counter substrate 11and liquid crystal layer 12 is reflected by the reflective electrode 23,and selectively emitted from the counter substrate 11, and an image isdisplayed.

[0130] Moreover, when this semi-transmission type liquid crystal displaydevice is utilized as a transmission type, a back light incident fromthe back light unit 42 via the array substrate 10 is selectively emittedfrom the counter substrate 11 via the hole for transmission 23 e, andthe image is displayed.

[0131] The semi-transmission type liquid crystal display device ismanufactured as follows. That is, similarly as the first embodiment,after the steps shown in FIGS. 14A to 14G are performed, a transparentconductive film, for example, of ITO is formed on the organic insulatingfilm 26 in a thickness of about 100 nm by the sputtering process, andpatterned into the predetermined shape by the photo-etching process, sothat the transparent pixel electrode 23 f is formed. Thereafter, asshown in FIG. 14H, the reflective pixel electrode 23 having the hole fortransmission 23 e is formed. The subsequent steps are similar to thoseof the fifth embodiment.

[0132] Even in the semi-transmission type liquid crystal display deviceconstituted as described above, the effect similar to that of the fifthembodiment is obtained. Moreover, when the display device is utilized asthe transmission type, an electric field acting on the liquid crystallayer 12 is raised in a transmission area in the vicinity of the holefor transmission 23 e. That is, as compared with the fifth embodiment,the electric field between the transparent pixel electrode 23 f and thecounter electrode 38 directly acts on the liquid crystal layer 12,because the transparent pixel electrode 23 f is disposed opposite to thehole for transmission 23 e. Therefore, when the display device isutilized as the transmission type, the contrast is increased, and it ispossible to obtain a satisfactory liquid crystal display device having asatisfactory display quality.

[0133] The semi-transmission type liquid crystal display deviceaccording to a seventh embodiment will next be described.

[0134]FIG. 16 shows the sectional structure of the semi-transmissiontype liquid crystal display device. The semi-transmission type liquidcrystal display device is constituted similarly as the sixth embodimentshown in FIG. 15 excluding the following structure. Therefore, in FIG.16, a part similar to that of the sixth embodiment is denoted with thesame reference numeral, and the description thereof is omitted.

[0135] In the semi-transmission type liquid crystal display device, asshown in FIG. 16, the transparent pixel electrode 23 f formed by thetransparent conductive member such as ITO is disposed in the areacorresponding to the hole for transmission 23 e of the reflective pixelelectrode 23. The organic insulating film 26 having concave/convex isremoved, and the flatted protective insulating film 25 is disposed asthe substrate in the area corresponding to the hole for transmission 23e. The transparent pixel electrode 23 f is disposed on the protectiveinsulating film 25.

[0136] Moreover, the semi-transmission type liquid crystal displaydevice includes the back light unit 42 for lighting from the side of thearray substrate 10. Furthermore, the semi-transmission type liquidcrystal display device includes the polarization plate 41 on the surfaceof the array substrate 10 disposed opposite to the back light unit 42.For example, the polarization plate 41 is disposed such that thepolarization surface crosses at right angles to the polarization plate40 disposed on the opposite substrate 11.

[0137] The semi-transmission type liquid crystal display device ismanufactured as follows. That is, similarly as the first embodiment,after the steps shown in FIGS. 14A to 14G are performed, a part of theorganic insulating film 26 is removed by the photo-etching process and apart of the protective insulating film 25 is exposed. Subsequently, thetransparent conductive film, for example, of ITO is formed on theorganic insulating film 26 and protective insulating film 25 in athickness of about 100 nm by the sputtering process, and patterned intothe predetermined shape by the photo-etching process, so that thetransparent pixel electrode 23 f is formed. Thereafter, as shown in FIG.14H, the reflective pixel electrode 23 having the hole for transmission23 e is formed in the area from which the organic insulating film 26 isremoved. The subsequent steps are similar to those of the fifthembodiment.

[0138] Even in the semi-transmission type liquid crystal display deviceconstituted as described above, the effect similar to that of the fifthembodiment is obtained. Moreover, the thickness of each liquid crystallayer 12 in the transmission and reflective areas can independently becontrolled. Therefore, when the display device is utilized as thetransmission or reflective type, an optical condition can be optimized.In each case, it is possible to obtain the satisfactory liquid crystaldisplay device having the satisfactory display quality.

[0139] Additional advantages and modifications will readily occur tothose skilled in the art. Therefore, the invention in its broaderaspects is not limited to the specific details and representativeembodiments shown and described herein. Accordingly, variousmodifications may be made without departing from the spirit or scope ofthe general invention concept as defined by the appended claims andtheir equivalents.

What is claimed is:
 1. A liquid crystal display device comprising: afirst and second electrode substrates; and a liquid crystal layer whichis held between said first and second electrode substrates and whoseliquid crystal molecular arrangement is divided into a plurality ofpixel areas controlled by said first and second electrode substrates,wherein said first electrode substrate includes a reflective plate forscattering a light incident via said second electrode substrate and saidliquid crystal layer, and said reflective plate has a reflective surfacein which a first undulation formed by disposing a gradual inclinedsurface in each pixel area and a second undulation formed by disposing aplurality of main scattering portions in each pixel area aresuperimposed.
 2. The liquid crystal display device according to claim 1,wherein said first electrode substrate includes a plurality of pixelelectrodes for applying a pixel potential to each corresponding pixelarea, and said second undulation is disposed in the reflective surfaceexcluding a gap between the pixel electrodes.
 3. The liquid crystaldisplay device according to claim 2, wherein said reflective plate isconstituted of said plurality of pixel electrodes.
 4. The liquid crystaldisplay device according to claim 1, wherein said first electrodesubstrate includes an insulating layer as a substrate of said reflectiveplate.
 5. The liquid crystal display device according to claim 4,wherein said first electrode substrate includes a wiring member coatedwith said insulating layer, and an inclination angle of said firstundulation depends on a thickness of said wiring member.
 6. The liquidcrystal display device according to claim 4, wherein said firstelectrode substrate includes a wiring member coated with said insulatinglayer, and said main scattering portion is disposed in the reflectivesurface excluding a position above said wiring member.
 7. The liquidcrystal display device according to claim 4, wherein said insulatinglayer includes an organic insulating layer which defines said firstundulation and said second undulation.
 8. The liquid crystal displaydevice according to claim 7, wherein said organic insulating layer isconstituted of a photosensitive resin.
 9. The liquid crystal displaydevice according to claim 7, wherein said organic insulating layerincludes a laminate of a first organic insulating film which definessaid first undulation and a second organic insulating film which definessaid second undulation.
 10. The liquid crystal display device accordingto claim 9, wherein each of said first organic insulating film and saidsecond organic insulating film is constituted of a photosensitive resin.11. The liquid crystal display device according to claim 7, wherein saidinsulating layer further includes an inorganic insulating layer as asubstrate of said organic insulating layer.
 12. The liquid crystaldisplay device according to claim 11, wherein said inorganic insulatinglayer includes a plurality of island portions disposed inside an outeredge of each pixel area, and an inclination angle of said firstundulation depends on a thickness of said plurality of island portions.13. The liquid crystal display device according to claim 1, wherein eachmain scattering portion is a randomly disposed convex portion.
 14. Theliquid crystal display device according to claim 1, wherein each mainscattering portion is a randomly disposed concave portion.
 15. A liquidcrystal display device comprising: first and second electrodesubstrates; and a liquid crystal layer which is held between said firstand second electrode substrates and whose liquid crystal moleculararrangement is divided into a plurality of pixel areas controlled bysaid first and second electrode substrates, wherein said first electrodesubstrate includes an area in which a reflective plate for scattering alight incident via said second electrode substrate and said liquidcrystal layer is formed and which has a reflection function, and an areahaving a transmission function for transmitting the light incident viasaid first electrode substrate, and said reflective plate has areflective surface in which a first undulation formed by disposing agradual inclined surface in each pixel area and a second undulationformed by disposing a plurality of main scattering portions in eachpixel area are superimposed.
 16. The liquid crystal display deviceaccording to claim 15, wherein the area having said transmissionfunction has a hole for transmission in said reflective plate.
 17. Theliquid crystal display device according to claim 15, wherein an areahaving said transmission function has a plurality of transparentelectrodes for applying a pixel potential to each corresponding pixelarea.
 18. The liquid crystal display device according to claim 17,wherein said transparent electrode is disposed on an insulating layerhaving concave/convex.
 19. The liquid crystal display device accordingto claim 18, wherein said insulating layer includes an organicinsulating layer which defines said first undulation and said secondundulation.
 20. The liquid crystal display device according to claim 19,wherein said organic insulating layer is constituted of a photosensitiveresin.
 21. The liquid crystal display device according to claim 17,wherein said transparent electrode is disposed on a flatted insulatinglayer.
 22. The liquid crystal display device according to claim 21,wherein said insulating layer includes an organic insulating layer, andan inorganic insulating layer as a substrate of the organic insulatinglayer, and said transparent electrode is disposed on the inorganicinsulating layer.